1. Field of the Invention
This invention relates to apparatus for projecting a real, two-dimensional image of a section of a scene recorded on a hologram and more particularly to such a projector which is adjustable to allow modification of the section of the stored information which is projected.
2. Prior Art
When a hologram is illuminated with an appropriate reconstructing light beam the fringes refract the light to produce both virtual and real images of the recorded wavefronts. An observer looking through the illuminated hologram sees the virtual image and to observe a screened projection of the recorded wavefronts the conjugate or real image is typically projected on a screen. The resulting projected image had to be of the same size as the original. If an attempt was made to magnify the image by using an illuminating beam having a different degree of divergence than the reference beam which was used to form the hologram the resulting image would be aberrated. Accordingly, viewing the real image as projected on a screen may represent a useful technique for a single observer but is not suitable for group presentations. Use of the projected conjugate image also presents difficulties in that the position of the screen relative to the hologram must be varied in order to view the reconstructed image from different angles or to view a different plane in the object.
The present invention is broadly directed toward a system for projecting real images recorded on holograms which overcomes these limitations of previous techniques and provides much more versatility in terms of variations in the projected image.